Clip machines of the specified kind are used typically for closing packaging cases in bag or tubular shape which are filled with liquid to firm pasty or even (partly) granular content. In that procedure firstly the filling material is introduced into the packaging case and—in the case of a tubular packaging case—thereafter divided up into portions (sausages) by means of displacement elements. For that purpose the displacement elements constrict the packaging case in the radial direction and displace the filling material in the constriction region in the axial direction—with respect to the tube axis. A tubular plaited end portion is thus formed in the constriction region. In the next working cycle one or in the case of a dual clip arrangement two closure elements are applied to the tubular plaited end portion formed in that way, in mutually juxtaposed relationship, by means of the mutually movable closure tools described in the opening part of this specification.
The closure tools respectively include in paired relationship a male die and a female die, between which the clip is shaped around the packaging case during the closure operation until the minimum spacing of the closure tools is reached (closure spacing). After the closure operation the closure tools are moved back into their starting or open position.
High demands are made in terms of the quality of such a closure. On the other hand it is not to be so firm that the packaging case is damaged in the closure operation. On the other hand however the closure must be of sufficient sealing integrity so that for example in subsequent treatment of the closed sausage (cooking, smoking etc) it does not slip off the packaging case. If the clip machine is to be used for a large number of different sausage products and packaging cases, different clips are therefore used, which differ both in respect of their strength and also their size (limb length and material thickness). In general terms therefore in most cases at least one of the closure tools is also interchangeable and closure tools which are suitably matched to the respective size of the clip being used are employed in order to achieve precisely defined deformation of the clip in the closure operation.
The interchangeable closure tool is generally the female die which can be fitted into a (accurately fitting) female die holder and fixed therein. Hereinafter therefore reference is made to the first closure tool or the die, as being synonymous.
Interchangeability of the closure tool however basically entails the risk that, after a change in the clip, either it is forgotten that the compatible closure tool is used or by mistake a wrong closure tool is selected.
Because of differing material thickness different clips also involve different clip heights in the closed condition. It is therefore necessary for the rest position of at least one of the closure tools to be so adjusted that the closure spacing thereof is suited to the corresponding clip height. That is generally effected manually after each change in clip or each change in the interchangeable closure tool.
If suitable setting is not effected the consequence of that incorrect manipulation can be on the one hand that the set closure spacing is excessively great and the closure does not therefore attain the required level of strength. If on the other hand the set closure spacing is excessively small, the clip is closed too tightly around the tubular case and the tubular case can be damaged and/or an increased level of wear occurs at the moving parts of the clip machine and the closure tools and/or the clip machine is seriously damaged.